The present invention relates to the field of semiconductor devices. More specifically, the present invention relates to an apparatus and method for reducing layer separation and cracking in semiconductor devices.
In conventional semiconductor device fabrication processes, probe pads are used for electrically testing individual die. These probe pads are typically located within scribe streets that extend between individual die. However, when probe pads are located in scribe streets that are narrow, the probe pads and the underlying metal layers that couple to the probe pads can be cut by the sawing process that is used for separating the die.
When the probe pads and the underlying metal layers are cut by the sawing process, layer separation and cracking can result. More particularly, the upward movement of the back of the blade exerts a force against the probe pads and the underlying metal layers that can cause the probe pads and/or the underlying metal layers to separate or crack.
The layer separation and/or cracks often do not extend beyond the scribe street area, leaving the inner part of the die intact. However, subsequent process steps can cause the layer separation and/or the cracks to propagate into the inner part of the die. When the layer separation and/or the cracks propagate into the inner part of the die, device failure can result.
The subsequent process steps for forming a ball grid array device can cause the layer separation and/or the cracks to propagate into the inner part of the die. For example, process steps that apply stress to the die, such as steps in which the die is handled, can cause the layer separation and/or cracks to propagate into the inner part of the die. Also, process steps that include heating (e.g., wire bonding processes and adhesive curing processes) can cause the layer separation and/or the cracks to propagate into the inner part of the die.
In addition, the layer separation and/or the cracks can propagate during reliability test procedures. This can cause reliability-test failures. These reliability-test failures indicate likely failure during subsequent operation and usage of the device.
Thus, there is a need for a semiconductor device and a method for forming a semiconductor device having reduced layer separation and cracking. In addition, there is a need for a ball grid array device and a method for forming a ball grid array device having reduced layer separation and cracking. The present invention meets the above needs.
The present invention provides a semiconductor device and a method for forming a semiconductor device having reduced layer separation and cracking. In addition, the present invention provides a ball grid array device and a method for forming a ball grid array device having reduced layer separation and cracking. By reducing layer separation and cracking, a semiconductor device and a ball grid array device are obtained that have fewer device failures and fewer reliability problems.
A method for forming a semiconductor device in which layer separation and cracking is reduced is disclosed. A structure is formed over a semiconductor wafer that includes die separated by scribe streets and that includes probe pads for testing die. These probe pads are electrically coupled to the die by metal layers that at least partially underlie the probe pads. A notch is cut within a scribe street using a first cutting blade having cutting surfaces disposed at an acute angle relative to the center axis of the cutting blade. This removes portions of at least some of the probe pads and removes portions of at least some of the underlying metal layers so as to expose an open area that does not, contain any remaining portion of the probe pads and that does not contain any remaining portion of the metal layers. Because the cutting surfaces are disposed at an acute angle, less vertical force is applied by the rear edge of the cutting blade. Accordingly, less separation and cracking results.
The wafer is then severed by extending a second cutting blade into the open area. Because the wafer is severed within the open area, the second cutting blade does not contact any remaining portion of a probe pad or any remaining portion of a metal layer. Therefore, layer separation and cracking does not occur during the severing process. Accordingly, the present method produces a semiconductor device having reduced layer separation and cracking.
Also, a method for forming a ball grid array device is disclosed. First, a semiconductor device is formed in accordance with the method for forming a semiconductor device in which layer separation and cracking is reduced. The semiconductor device is attached to a ball grid array package substrate using adhesive. Wire bonds are coupled to the semiconductor device and are coupled to the ball grid array package substrate so as to electrically couple the semiconductor device to the ball grid array package substrate. Encapsulant is then disposed over the ball grid array package substrate and is cured to complete the ball grid array device.
These and other advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiments, which are illustrated in the various drawing figures.